如何在searchDelegate上突出显示正确的单词？

class MySearchDelegate extends SearchDelegate<String> {
  @override
  List<Widget> buildActions(BuildContext context) {
    return [
      IconButton(
        icon: Icon(Icons.clear),
        onPressed: () {
          query = '';
        },
      ),
    ];
  }

  @override
  Widget buildLeading(BuildContext context) {
    return IconButton(
      icon: Icon(Icons.arrow_back),
      onPressed: () {
        close(context, '');
      },
    );
  }

  @override
  Widget buildResults(BuildContext context) {
    // 根据query进行搜索逻辑，获取搜索结果列表

    List<String> searchResults = ['Hello', 'World', 'Flutter'];

    return ListView.builder(
      itemCount: searchResults.length,
      itemBuilder: (context, index) {
        String result = searchResults[index];

        // 根据query来突出显示正确的单词
        TextSpan textSpan = highlightOccurrences(result, query);

        return ListTile(
          title: RichText(
            text: textSpan,
          ),
          onTap: () {
            close(context, result);
          },
        );
      },
    );
  }

  TextSpan highlightOccurrences(String text, String query) {
    if (query.isEmpty) {
      return TextSpan(text: text);
    }

    List<String> queryWords = query.split(' ');
    List<TextSpan> textSpans = [];

    for (String word in queryWords) {
      RegExp regExp = RegExp(word, caseSensitive: false);
      Iterable<Match> matches = regExp.allMatches(text);

      for (Match match in matches) {
        textSpans.add(
          TextSpan(
            text: match.group(0),
            style: TextStyle(
              fontWeight: FontWeight.bold,
            ),
          ),
        );
      }
    }

    if (textSpans.isEmpty) {
      return TextSpan(text: text);
    }

    return TextSpan(children: textSpans);
  }

  @override
  Widget buildSuggestions(BuildContext context) {
    return Container();
  }
}